Geometry With Only a Compass
17 Aug 2011
Puzzle

Using only a compass (and without a straight edge or a ruler), is it possible to identify (a) the midpoint of two points? (b) the center of a circle? (c) all four corners of a square, given two of them?

Source

Heard when I was preparing for IIT-JEE in 1990.

Solution

Cut The Knot article describes several such constructions.

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